/************************************************************

  This example shows how to read and write bitfield
  datatypes to an attribute.  The program first writes bit
  fields to an attribute with a dataspace of DIM0xDIM1, then
  closes the file.  Next, it reopens the file, reads back
  the data, and outputs it to the screen.

  This file is intended for use with HDF5 Library version 1.8

 ************************************************************/

#include "hdf5.h"
#include <stdio.h>
#include <stdlib.h>

#define FILE            "h5ex_t_bitatt.h5"
#define DATASET         "DS1"
#define ATTRIBUTE       "A1"
#define DIM0            4
#define DIM1            7

int
main (void)
{
    hid_t           file, space, dset, attr;    /* Handles */
    herr_t          status;
    hsize_t         dims[2] = {DIM0, DIM1};
    unsigned char   wdata[DIM0][DIM1],          /* Write buffer */
                    **rdata;                    /* Read buffer */
    int             ndims, A, B, C, D,
                    i, j;

    /*
     * Initialize data.  We will manually pack 4 2-bit integers into
     * each unsigned char data element.
     */
    for (i=0; i<DIM0; i++)
        for (j=0; j<DIM1; j++) {
            wdata[i][j] = 0;
            wdata[i][j] |= (i * j - j) & 0x03;          /* Field "A" */
            wdata[i][j] |= (i & 0x03) << 2;             /* Field "B" */
            wdata[i][j] |= (j & 0x03) << 4;             /* Field "C" */
            wdata[i][j] |= ( (i + j) & 0x03 ) <<6;      /* Field "D" */
        }

    /*
     * Create a new file using the default properties.
     */
    file = H5Fcreate (FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);

    /*
     * Create dataset with a null dataspace.
     */
    space = H5Screate (H5S_NULL);
    dset = H5Dcreate (file, DATASET, H5T_STD_I32LE, space, H5P_DEFAULT,
                H5P_DEFAULT, H5P_DEFAULT);
    status = H5Sclose (space);

    /*
     * Create dataspace.  Setting maximum size to NULL sets the maximum
     * size to be the current size.
     */
    space = H5Screate_simple (2, dims, NULL);

    /*
     * Create the attribute and write the bitfield data to it.
     */
    attr = H5Acreate (dset, ATTRIBUTE, H5T_STD_B8BE, space, H5P_DEFAULT,
                H5P_DEFAULT);
    status = H5Awrite (attr, H5T_NATIVE_B8, wdata[0]);

    /*
     * Close and release resources.
     */
    status = H5Aclose (attr);
    status = H5Dclose (dset);
    status = H5Sclose (space);
    status = H5Fclose (file);


    /*
     * Now we begin the read section of this example.  Here we assume
     * the attribute has the same name and rank, but can have any size.
     * Therefore we must allocate a new array to read in data using
     * malloc().
     */

    /*
     * Open file, dataset, and attribute.
     */
    file = H5Fopen (FILE, H5F_ACC_RDONLY, H5P_DEFAULT);
    dset = H5Dopen (file, DATASET, H5P_DEFAULT);
    attr = H5Aopen (dset, ATTRIBUTE, H5P_DEFAULT);

    /*
     * Get dataspace and allocate memory for read buffer.  This is a
     * two dimensional attribute so the dynamic allocation must be done
     * in steps.
     */
    space = H5Aget_space (attr);
    ndims = H5Sget_simple_extent_dims (space, dims, NULL);

    /*
     * Allocate array of pointers to rows.
     */
    rdata = (unsigned char **) malloc (dims[0] * sizeof (unsigned char *));

    /*
     * Allocate space for bitfield data.
     */
    rdata[0] = (unsigned char *) malloc (dims[0] * dims[1] *
                sizeof (unsigned char));

    /*
     * Set the rest of the pointers to rows to the correct addresses.
     */
    for (i=1; i<dims[0]; i++)
        rdata[i] = rdata[0] + i * dims[1];

    /*
     * Read the data.
     */
    status = H5Aread (attr, H5T_NATIVE_B8, rdata[0]);

    /*
     * Output the data to the screen.
     */
    printf ("%s:\n", ATTRIBUTE);
    for (i=0; i<dims[0]; i++) {
        printf (" [");
        for (j=0; j<dims[1]; j++){
            A = rdata[i][j] & 0x03;         /* Retrieve field "A" */
            B = (rdata[i][j] >> 2) & 0x03;  /* Retrieve field "B" */
            C = (rdata[i][j] >> 4) & 0x03;  /* Retrieve field "C" */
            D = (rdata[i][j] >> 6) & 0x03;  /* Retrieve field "D" */
            printf (" {%d, %d, %d, %d}", A, B, C, D);
        }
        printf (" ]\n");
    }

    /*
     * Close and release resources.
     */
    free (rdata[0]);
    free (rdata);
    status = H5Aclose (attr);
    status = H5Dclose (dset);
    status = H5Sclose (space);
    status = H5Fclose (file);

    return 0;
}
